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Dale Lawrence
Professor, Smead Aerospace
Wednesday, Feb. 26 | 1:45 P.M. | AERO 111

Abstract: A system of balloon-borne instruments to conduct descending (wake free) measurements of fine-scale turbulence is described, developed as part of an AFOSR Multi-University Research Initiative called HYFLITS (HYpersonic Flight In the Turbulent Stratosphere).�� The system consists of custom high-rate hotwire anemometer and coldwire thermometer, integrated with a commercial radiosonde and a particle sensor, and GPS position and velocity sensing and radio telemetry in a small gondola. The balloon apogee and descent rate are controlled via a custom venting valve in the neck of the balloon to release lifting gas. A custom ground station equipped with an automatic balloon tracking high-gain antenna receives the telemetered measurement data. Development of this system focused on accessing altitudes of interest in the stratosphere for future hypersonic vehicles and to facilitate numerous turbulence observations by lowering the cost of equipment and flight operations. The system is also lightweight enough to be classified as an “unregulated” free balloon in the US and a “light” free balloon in Europe, reducing obstacles due to airspace regulations.

The HYFLITS system has been used in an extended campaign to conduct more than 200 flights observing turbulent kinetic energy dissipation rate (e) and temperature structure function parameter (C_T²) with 5m vertical resolution in flights descending from up to 33km and down to 3km. Flights have occurred in Colorado, Minnesota, Florida, Virginia (NASA Wallops), northern Sweden (Esrange), Antarctica (Syowa Station) and Indonesia (Kototabang).

This talk will discuss details of the observation system and its operation, overview the observations to date, and provide an outline of the data reduction and calibration methods used to obtain e and C_T² characterization of turbulence from telemetered data.

Bio: Dale Lawrence has worked most of his career at the intersection of dynamics/control theory and practical applications. This work has been driven by interest in a variety of applications, available funding opportunities, and collaboration with students and colleagues, which has resulted in contributions over a rather eclectic range of problems in system identification and adaptive control, disk drives, tele- and micro-robotics, haptic interfaces, line-of-sight stabilization, solar sail spacecraft, small UAV design and control, and most recently, measurement of atmospheric turbulence and UAV precision landing.��

Professor Lawrence received a B.S. from Colorado State University, and a M.S. and Ph.D. from Cornell University. Subsequently he worked for Martin Marietta Astronautics (now Lockheed Martin) and returned to academia at the University of Cincinnati before joining the University of Colorado in 1991. He is currently a Professor in the Smead Aerospace Engineering Sciences Department.��
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